diff --git a/CMakeLists.txt b/CMakeLists.txt
index b70b540..afa94f0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,6 +2,7 @@ cmake_minimum_required(VERSION 3.5.1)
 project(CrossGuid)
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${PROJECT_SOURCE_DIR}/cmake")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O3")
 
 option(XG_TESTS "Build test runner" ON)
 
diff --git a/Guid.cpp b/Guid.cpp
index bd8c61c..ca0c6be 100644
--- a/Guid.cpp
+++ b/Guid.cpp
@@ -184,7 +184,8 @@ unsigned char hexPairToChar(char a, char b)
 // create a guid from string
 Guid::Guid(const std::string &fromString)
 {
-	char charOne, charTwo;
+	char charOne = '\0';
+	char charTwo = '\0';
 	bool lookingForFirstChar = true;
 	unsigned nextByte = 0;